1. Field of the Invention
The present invention relates to a silicone gel composition excellent in damping properties.
2. Description of the Prior Art
Hitherto, silicone gellike cured products, i.e., silicone gels are given electric resistance properties and heat dissipation properties and are then used in filling elements such as HIC (hybrid IC) and power modules to protect them. In this application, silicone gels are demanded to be improved in rapid curability which allows the silicone gel to be cured in a short period of time to produce the element efficiently and in low-temperature properties which keep elastic properties even at a low temperature, for example, of about -60.degree. C. and secure high reliability against environments of the application in which the assembled product is used as well as in damping properties for improving vibrating stress resistance of the parts having the elements.
It is known that organopolysiloxanes having CH.sub.3 SiO.sub.1.5 units are good in low-temperature properties, and silicone gel compositions having a base component an organopolysiloxane substantially comprising 80 to 96.5 mol % of (CH.sub.3).sub.2 SiO units, 2.0 to 10.0 mol % of CH.sub.3 SiO.sub.1.5 units, 0.25 to 4.0 mol % of (CH.sub.3).sub.2 (CH.sub.2 .dbd.CH)SiO.sub.0.5 units, and 25 to 6.0 mol % of (CH.sub.3).sub.3 SiO.sub.0.5 units are disclosed, for example, in Japanese Pre-examination Patent Publication (kokai) Nos. 58-7452 (1983) and 62-20557 (1987).
Further, the above Japanese Pre-examination Patent Publication (kokai) No. 58-7452 (1983) describes that it is indispensable for a rapid curing reaction that the above organopolysiloxane has (CH.sub.3).sub.2 (CH.sub.2 .dbd.CH)SiO.sub.0.5 units as crosslinking groups for the curing reaction. The above Japanese Pre-examination Patent Publication (kokai) No. 62-20557 (1987) teaches that although the use of a specific amino compound as a reaction retarding agent is useful, even in the case wherein such a reaction retarding agent is used, the pot life of the composition can be remarkably shortened by the blending of a silica processed, for example, with trimethylsilyl groups.
Further, Japanese Pre-examination Patent Publication (kokai) No. 62-181357 (1987) discloses as a composition improved in stability against discoloration and change of hardness due to heat deterioration and stability against adhesiveness a composition comprising (a) 10 to 70 parts by weight of an organopolysiloxane substantially comprising 80 to 98.75 mol % of (CH.sub.3).sub.2 SiO units, 1.0 to 10.0 mol % of CH.sub.3 SiO.sub.1.5 units, 0.25 to 4.0 mol % of (CH.sub.3).sub.2 (CH.sub.2 .dbd.CH)SiO.sub.0.5 units, and 0 to 6.0 mol % of (CH.sub.3).sub.3 SiO.sub.0.5 units and having a viscosity of 20 to 10,000 cSt at a temperature of 25.degree. C. and (b) 30 to 90 parts by weight of a polydiorganosiloxane whose both ends are blocked with vinyl groups and which has a viscosity of 100 to 100,000 cSt at 25.degree. C. and is basically linear.
However, silicone gels obtained from these known silicone gel compositions cannot satisfy all the demanded properties such as good low-temperature properties and excellent damping properties and cannot satisfy requirements in the above application because, for example, they are slow in curing speed.